The purpose of this study is to determine the relative roles of the testicular steroid and peptide hormones in the control of secretion of the pituitary hormones LH and FSH in the human male. Prior to processing samples available to the investigators from previous admissions, it will be crucial to demonstrate that inhibin is stable in serum a/o plasma when frozen. The investigators preliminary communication with the only group with a sensitive and specific assay for inhibin, which employs identical methods to those they are currently using, suggests that inhibin is stable in serum with freezing and thawing (c. Rivier, personal communication). However, this fact will be first ascertained in their assay. Should freezing/thawing stability not prove to be the case, then this section will be performed on fresh specimens or, more likely, on specimens whose collection and preservation conditions have been optimized to prepare inhibin for the investigators assay conditions. Having optimized assays conditions and sample processing techniques, serum pools from each circumstance cited above will be examined in the assay for the presence or absence of inhibin. Once inhibin has been detected, all the time points from individual dmissions will similarly be examined to gain some insight into the apparent half-life of this compund. In this regard, the admissions with decreasing frequency of GnRH administration, particularly those employing an 8 hourly interval of stimulation, should be useful in establishing the minimal frequency of sampling required to permit an accurate, but economical, chronicling of the ontogeny of inhibin secretion and its correlation with gonadal size, FSH secretion, and maturation of spermatogenesis with serum levels. Since all these lines of data may already be available from the serum samples collected in the investigators previous studies, use of the IHH model whose sexual development has been controlled and charted in detail by monthly admissions represents an unusually efficient manner of gaining a considerable degree of early insight into its role in FSH regulation in the human male.